1. Field of the Invention
The present invention relates to a method of producing electrical resonant circuits, specifically of resonance labels for use in a theft protection system in which a coil and a capacitor located on a dielectric form a respective resonant circuit, where the coil having the shape of a spiral and forming one surface of the capacitor is located in the one side and the second surface of the capacitor is located at the other side of the dielectric.
2. Description of the Prior Art
Electrical resonant circuits of this kind placed onto a supporting foil and thereafter treated further in order to be used as adhesive labels or hard shells of a plastic material in a theft protection system have until now been produced predominantly by means of an etching, method in which the base material consists of two aluminum foils separated from each other by a non-conductive layer such as a plastic material, and in which by means of a printing of an etching medium resistant lacquer onto the two aluminum foils the desired shape of the resonant circuit consisting of a coil and a capacitor is set. When the undesired parts of the aluminum foil are removed by the etching procedure a coil in shape of a planar spiral and a first capacitor surface as well remain on the one side of the supporting foil and a second capacitor surface is produced by the etching procedure on the other side of the supporting foil which still is to be electrically connected to the first one.
In order to produce these known resonance labels predominantly aluminum foil is used for cost reasons and after this producing it is necessary to dispose of the etching slurry which remains after the etching process which must be done in consideration of pollution control which at the present is given special attention. Non-polluting disposal leads to not negletable higher costs.